Production of high molecular weight elastic hydrocarbon polymers



Ap 7, 1953 w. F. FARAGHER PRODUCTION OF HIGH MOLECULAR WEIGHT ELASTIC HYDROCARBON POLYMERS 2 SHEETS- SHEET l Filed Sept. ll, 1951 April 7, 1953 w. F. FARAGHER PRODUCTION OF' HIGH MOLECULAR WEIGHT ELASTIC HYDROCARBON POLYMERS 2 SHEETS-SHEET 2 Filed Sept. ll. 1951 INVENTOR Frger BY AGENT Patented Apr. 7, 1953 PRODUCTION OF HIGH MOLECULAR WEIGHT ELASTIC HYDROCARBON POLYMERS Warren F. Faragher, Swarthmore, Pa., assgnor to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application September 11, 11951, Serial No. 245,999

Claims.

The present invention relates to new and improved methods for the production of synthetic -velastomers of a rubbery nature by the copolymerizaticn of a conjugated diolen, butadiene,

together with an aryl alkene-l, styrene, and is a continuation-impart of my copending application, Serial No. 95,691, led May 27, 1949 (now abandoned), which is a continuation-in-part of my application, Serial No. 582,358, led March l2, 1945, now Patent No. 2,502,444, issued April 4, 1950.

In accordance with the present invention, a high molecular weight elastomer or elastic hydrocarbon copolymer consisting of butadiene and styrene is produced under conditions such that cyclic dimer, l-ethenylcyclohexene; this cyclic dimer is thereafter dehydrogenated to form styrene which then is utilized as at least a portion Vof the styrene needed for the copolymer.

By proper selection of the conditions under which the polymerization is effected, suiiicent quantif polymerization is effected in an aromatic hydrocarbon solvent, ethylbenzene. Butadiene from line I@ is introduced by a variable delivery pump II to line I2 where 'it is mixed with styrene and ethylbenzene introduced from line I3 by a variable delvery pump It.V A catalyst, such as lead tetraethyl, nickel carbonyl, sodium, metal or other catalysts known to the art, may be added v.to the reactants in line I2 through line I5 as a solution or dispersion in a suitable medium such as ethylbenzene. The entire reaction mixture is Y then passed through a heat exchanger I6 to polymerization zone Il. The reactants are -then agitated in the polymerization zone by means Vof a vreciprocating valveless pump I8, the opposite rendsof pump I8 being cor'i'nected with the opposite ends of the lreaction zone so that whenthe piston of this'pump reciprocates, the liquid in the "reaction zones isalternately withdrawn and recharged at each end. Y, By such a pump, the desiredagitation can be maintained Within the reaction'zone Without extending the length of ,the freactionzone excessively. Thetemperature a portion of the butadiene polymerzes to form aV 2 and pressure in the polymerization zone are controlled by conventional equipment.

The reaction mixture, after polymerization, is

discharged through a pressure reducing valve I9 into a separation zone 2I Where separation of the elastomer or copolymer from volatile gaseous or relatively volatile liquid hydrocarbon constituents is effected by known methods such as ash or steam distillation. The separation zone,

if desired, may consist of two units, copolymer being removed from one zone While it is being separated from the other constituents in the other, or may be operated continuously, as in the case of flash distillation. The volatile gaseous and relatively volatile liquid hydrocarbon constituents, which comprise ethylbenzene, the cyclic dimer of butadiene (4-ethenylcyclohe`xene) and any unreacted butadiene or styrene, from separation zone 2I pass, by line 22, to a fractionation zone 23, valve 24 being open. In iractionation zone 23, unreacted butadiene is taken oi as an overhead fraction and forwarded to line I@ by line .25, valve 23 being open, so that lit is mixed' with fresh butadiene to be polymerized. If there is no butadiene present, fractionation zone 23 may be bypassed by opening valve 2, closing valve 24 and passing the mixture through line 28. A fraction containing ethylbenzene and cyclic dimer is removed iromgthe fractionation zone as a bottoms fraction and directed by line 29 to a dehydrogenation zone 3l, valve 32 being open. In the event that this fraction contains unreacted styrene, it is precyclic dimer are contacted with a dehydrogenaferred to send it to a supplementary fractionation zone 33, by closing valve 32 and opening valve 34. Afterseparation, the styrene is recycled back to the polymerization zone by lines 35 and I3 while the ethylbenzene and the cyclic dimer are forwarded to the dehydrogenation zone by line 36,'valve 3l being open.

In the dehydrogenation zone, ethylbenzene and tion catalyst, described more fully below, so as to form a mixture of styrene and ethylben'zene. By proper adjustment of the dehydrogenation conditions, the cyclic dimer is completely converted to ethylbenzene and/or styrene.- Since ethylbenzene is employed as thesolvent for the process, the advantage is gained that itis not necessary to dehydrogenate the cyclic dimer completely to styrene or to separate the styrene from the vless completely dehydrogenated product,

ethylbenzene. Furthermore, reactionlconditions f indehydrogenation'zone 3l maybe selected so 4.that a constant and desired ratio of styrene Y 3 to ethylbenzene is maintained in the effluent products.

The products of dehydrogenation pass through line 38 to a separation zone 39 where hydrogen is separated by known methods and apparatus (e. g., a'condensing gas separator) from the liquid dehydrogenation products. Liquid dehydrogenation products containing a mixture of styrene and ethylbenzene are pumped throughlines il and I3 thence to the polymerization,zonel or alternately part may be directed to storage zone 42.

The conditions of temperature andpressure employed in polymerizationzone Iljlaresuch that liquid or mixed phase conditions are maintained therein. In general, the temperature is preferably at an elevated temperature abovel roomtemperature, such as above about 100 F. to below about 400 F. Increased conversion to 'copoly- ,mers results when the temperature is in a preferred upper portion.; of this rangev (i. e., from about, ,150? F. to 350 F.) but is accompanied by an'increase in thewcyclic dimer. (The formation of Ithe, cyclicA dimer, 4ethenylcyclohexene, is

adequately discussed in an article by-R. F. Robey et al. appearing in Industrial and Engineering Chemistry, volume 36, page ,3,l January 1944.) The use of'a relatively high temperature is of ,considerable advantage in electing the copolymerizationat anV advantageously rapid rate but iis disadvantageous in that the cyclic dimer is 4formed asa byproduct to a considerable extent,

vi-,hereby substantially diminishing the yield of desired copolymer from a given amount of butadiene.

In thepresent invention, the disadvantageous formation of the cyclicdimer becomes an advantage and the conversion of butadiene to the copolymer is effected in an economical manner.

Frein. the data given in the'cited article, a tem- .'perature can be selected such that the amount fof ldi'mer formation is sufficient for the process to be, :self-sustaining (i. e., solely butadiene is c needed as ar'aw` material), or the polymerization may be'eiectedso as'to obtain greater and lesser Vx-amounts of cyclic dimer... In the event that lesser Afa'ifiiounts are obtained,v the deciency may be ,',n'ia'de up by styrene obtained 4from other sources;

when greater vamounts are formed, the cyclic ,dimer "sho obtained `can be dehydrogenated to styrene and employed for the making of styrene plastics.

y; ,Inl another embodiment of the invention illus- `stratediin Fig. 2, the copolymerization is effected in a manner known Ato the art and referred to as aqueous'emulsion copolymerization, from its .technique of disp-ersing droplets of the reactants inan agitated aqueous phase.V

Any suitable emulsifying agent, such as is such as glue, agar agar or starch. a a

The polymerization'is conducted in the pres- KVence of a knowncatalystfor' emulsion*V polymerization, as, for eXample,' `alkali metal and'alkali earth metal perox'i'des', perborates, orpersulfatesfe diazoamino benzene, benzoyl peroxide, gasoline In Fig. 2, the cyclic dimer, 4-ethenylcyclohexene, is introduced by line 5a to a catalytic dehydrogenation zone 5l wherein it is contacted under 4dehydrogenation conditions so as to form styrene andethylbenzene, as described below. The eiu- `ent product from dehydrogenation zone 5I passes through linejiZ toa flash distillation zone 53 in whichhydrogen gas is separated from the liquid hydrocarbon products. After removal of the hydrogen, lthe liquidhydrocarbon products pass through line 5t to distillation zone 55 and are distilled under conditions which minimize or preclude polymerization of the styrene (i. e., under vacuum 'and/or inthe presence of elementary sulfur). .Ethylbenzene is removed from distillation zone 55 as the overhead fraction and' is Vre- -V cycled to the dehydrogenation zone through lines Etf and 53. The-styrene is removed as a Ybottoms fractionand passes through lines 5'! andl 58 to an emulsication zone 55 together with fresh butadiene introducedby -li'ne ttor recycled butadiene from line t2, the relative amounts of these materials being controlled by valves 63, 5d Vand'i. Soap and catalyst solution o r suspension is added toV the reactants through line 663.- 'The emulsion Vfoi-merlin zone 5s passes through line''i to na polymerization zone c3 (which may be of the same type as vdescribed in connection with`Fig.`l)

whereinit is polymerizedunder liquid or mixed phase conditions on'a continuous orbatchwse basis.

The emulsion, 'after polymerization, is discharged through line E!! and a pressure reducing valve il into a separation zone 'l2 Where separation of any unreacted volatile butadiene is effected. Y 1 Y The relatively nonvolatile remainder of the reaction products passes by line 13 to a coagulation zone T4 in which zone the synthetic latex produced by the copolymerization'ofbutadiene and styrene is coagulated, such as by addingjan acid, for example, aceticacid. AIhel coagulated latex as Well as thesolution passes, through line 'i5 to a filtration zone 76 orja steam distillation zone TI, in which -coagulated latex is separated' from the supernatant liquid. .,(If desired the coagulation and filtration or steam distillation may be effected in the same apparatus.) The supernatant liquid, which comprises an aqueous-phase containing soap, catalyst and other added vInaterials, andan oil phase containing cyclic dimer vand. any unreacted styreneis subjected to decantation as in decantationzone i8, the oil phase being ,thereafterdirected, as ,by une 19, to a .distillation zone di in which cycli-c dimer is separated fromany unreacted styrene.v The dimer .is removedfrom theV distillation zone as an overhead fraction and .passes through lines 8 2and V 50 to the catalytic dehydrogeriation zoneiStyrene y Vis, removedYfromldistillation zione' Stasia" fraction and passes through VlinesA 83, f'L-Landf' Yfor recycle to the. i polymerization 5911?: 1 lnlfhe eventk that the ,copolv;,iierization'- iseiect d derconditions such that allnthestyrene 4 sumed, the `oil phase fromM decantation; zone l 'I8 canlbe sent directlyto dehydrogenation Qnefl Vwithout. Afurther processing, Xaser .iajemve minor amounts of contaminants that woldyaf- 4feet ,the catalyst dehydrogenation by ,closing valve 84 and opening valve 85. e e

I n ,connection with the processes shown in both vFigures 1 and; 2, the cyclic dimer of butadiene, 4-ethenylcyclohexene, may be dehydrogenated by either a one step or a two step operation so as to `lproduce a mixture of ethylbenzene and styrene. In thel two step method, the cyclic dimer ,is iirst` dehydrogenated to ethylbenzene such as Aby `contact rwith known dehydrogenation or arofmatization catalysts such as chromium oxide, vanadium oxide, molybdenum oxide and the like,

either alone or on a suitable carrier such as ac- ;,tivated alumina, zirconia,l bauxite, titania and thelike, at temperaturesin general above 500 F. `and below about 850 to 900 F.; the ethylben- 4zene soformed being thereafter contacted with the'same or a similar catalyst in a second step l at a temperature above 900 F. to less than 1250 at shorter contact times (i. e., higher space velocities) than in the rst'step so as to convert ethylbenzene to styrene.

y Excellent results can be obtained by oontactv,ing ethylbenzene with a dehydrogenation cata- .lyst Vunder conditions su-ch that not only is the 1 contact time of the hydrocarbons short but also such that the partial pressure of the products is .lowfln order to obtain these conditions, the

dehydrogenation can be effected under reduced pressure such as from 2 to 8 inches of mercury absolute or steam can be added to the hydrocarbons in the dehydrogenation zone either prior f to or at the time of the introduction of the hyidrocarbons to the dehydrogenation zone.

The amount of such steam preferably should be vsuch that the partialpressure reaction product is less than 0.5 atmosphere, such as 0.1 atmosphere, de- .sirable `amounts vof steam being between one to four times the weight of the hydrocarbon. Catalysts effective in the reduced pressure operation are `in general those used in the rst step. Ef-

Y fective catalysts forA the operation Vemploying steam are catalysts such as chromium oxide, 1roI1 oxide, magnesium oxide, activated charcoals,

aluminum or bauxites,especially effective catalysts comprising predominantly an oxide of zinc, 4beryllium, or'zirconium with about 5 to 25 per cent of iron oxide and smaller amounts of a promoter, such as an oxide of an alkali or alkaline `earth, and astabilizer such as an oxide of copper, silver, manganese, nickel, cerium and the The one step operation is operated under somewhat similar conditions to 'those of the second step otthetwo step operation. Typical conditions include temperatures in the range of about 1,100 to 1250? F.; operation at reduced pressures of less than 0.5- atm'osphere, contact time of less than seconds and space velocities in the range of 1 .tov 10 (volumes of liquid hydrocarbons fed per hour per volume of catalyst present). Itis preferableto avoid easily reducibleoxides in the catalyst *since vthese have a tendency to cause scission of the cycloalkene ring; suitable catalysts. areV oxides. of chromium, molybdenum, 'vanadium and uranium on carriers such as alumina, zirconia and titania.

Example I A mixture of` 37.5 parts butadiene, 12.5 parts styrene, 50 parts benzene and 1.0 part lead tetraethyl, each by weight, was subjected to continuous `polymerization at 350 F. for contact time of 2 hours. An analysis of the product as determined by distillation showed kthe conversion to 12% heavy polymer and the recovery of 34% vdimer based ontheamount of butadiene charged.

Example II A mixture of 100 parts by weight of butadiene and 100 parts of benzene withan added one part of lead tetraethyl were polymerized at 350 F. for 80 minutes. Analysis of the product showed 57% conversion to high molecular weight polymer and 35% conversion to dimer based on the lamount of butadiene charged.

. EramplerIII A hydrocarbon mixture of 52.5 parts of butadiene, 17.5 parts styrene and 30 parts benzene, each by weight was emulsied with 1.4 volumes of soapsolution per volume of hydrocarbons, (2.0 weight ratio of water to hydrocarbon) the soap solution containing 5 parts by weight of soap, 0.25

part potassium persulfate and 0,3 part dodecylmercaptan. The emulsion was passed through a reaction tube at 275 F. and 600 pounds pressure for 30 minutes. The high conversion to good vquality synthetic rubber-was accompanied by the production of appreciable amounts of butadiene dimer. v

- Example IV In a typical operation of a continuous recycle process, there was fed to a jacketed reaction tube equipped with a v-alveless reciprocating pump designedV for agitation ofthe contents of the tube, a mixture of 50 parts butadiene, 16.7 parts styrene and 33.3 parts benzene, each by weight, for continuous polymerization in the presence of 1% tetra-ethyl lead by weight of the butadiene and styrene. There is obtained 1l-l2% conversion ,l of the reactants to elastomer, 30% of the original butadiene charge being converted to dimer, and

46% being recoverable as the monomer.v Physical tests subsequently conducted on the vulcanized polymer -(50 /45#) were as follows:

Modulus-425 pounds per square inch Tensile-1550 pounds per square inch Elongation-760% ization reactor. Benzene, with a cut point of approximately 176-177 F., and styrene, with a out point of approximately 293 F., likewise arerecovered as separate fractions from the fractionating column, and each is returned to the source of supply of these materials for the polymerizationlstep. 5'.

-j L The aunar, as

, another `'fraction from the fractionation co1'umn `and having a out point ofrap- 'p'rioxirnately 2664 F.; is `separately"recovered" and sent to a dehydrogenation vessel wherein it is subjected to contact with a fixed bed of chromealumina catalyst (20% chromia on activated alumina) at 1175 F., under a pressure of 0.1 atmosphere, and at a liquid hourly space velocity of 1.5, under which conditions approximately 35% of the dimer is converted to styrene. The styrene thus obtained is separated from the reaction products by distillation and the recovered 'Soppe thereof adftherefo'reonlysuch limitations shouldbe 'imposed as 'are "intimated in the" ap- 1. In a process for the `p1oduction"of"ahigh molecular weight-elastic hydrocarbon copolymei` 9lng Qf "buadin and. styrene. wherein .butadiene .'edfzsfrrne"efplymfizd ufdef liquid-phase conditionsiin a polymerization zone iproveinent Which comprises' effecting saidlpolybutadiene to '{l ethenylcyc1ohexene, separating from said hydrocarbon mixture a yolatile n orduced by dimerization of butadiene, forming styrene byl dehydrogenation of said normally liquid fraction-,fand introducir'f,r yto said? polymer- "ization 'zone jstyr'feifle''A formed by dehydrogenat'ion 'fof said normally liquid'- fraction as at 'least a" Dortion "off tliestyl l high molecular weightl elastic copolymer.

22. ma proessifritiie production of einen l molecular YWeight" elastic hydrocarbonv copolymer "consisting `of butadieiieand styrene wherein butadieneahd 'styreneaiepolymerase@ under liquid phase""oonditiosf'infapolynerization' zone-'sofas kto form a hydrocarbon mixturef comprising` substantialamonts ofsaid oopolymer, the Airripro'vement *Whielr comprises yeffecting :said polymer# l zene and styrene formed' by dehydrogenation'and said unreacted styrene as thevsolej sourceof the styrene copolymerizedto form'said high molecular weight elasticcopolymer.

3. Ina process for the production of Va high molecularfvveight elastic hydrocarbon copolymer consisting? of butadie'neand styrene vvhereinbutadiene and styrene are'polymerized under liquid phase conditionsin a polymerizationzone'fso'as to form ahydrocarbonmixture comprising substantialamounts of said copolymer, the improve-v T8 "nientwliichf-contpises-leiffeotingsaidfaolyirierization at a temperature finftle'rangeffiabout- 100 to '-4OOVA`" F. jAs ian aqueous mulsion-fand fooncomitantly"dimerizirigl a portion of saidvbta'diene f to l-ethenylcyclohexene, separating l from Jsaid hydrocarbon mixture 4-ethenylcyclohexene p-rofdu'cedby'dimerization ofbutadiene, forminglstyrene byfdehydroge'nation of said i-"ethenylcy'clohexene, 'fandV introducing `--said styrene -iorme'd by l 10 "dehydrogenation ofisaid 4-ethenylc`yclohexene. to fsaid'VY polymerization-1 zone fas" at 'least a portion of lthe styrene copolymerized to'l 'form said `high fino- "iecuiareweight elastiecopolymer.

A. in ia' process for the? production of a i high molecular Weight elastic-'f-hydrocarbon'fcopolymer 'feonsi'stirig of butadiene and styrene-wherein butadiene :fandstyrene arepolymerizedfunder@ liquid f'phase" onditionsfinja 'polymerization zonesoas to'- Vform-"1a hydrocarbon v mix-ture- 'cor'n`pr-i`si'n'i;y subtantial amounts -of 'said' copolymer; `the 'improve- 'me'htfoff'eiployigy butadiene as the Sole hydrocarbon raw material fori the 'production' of 'said 'copolymer whichl 'comprises e'iecting 'sai'dpoly- 'Amerizationata temp'eratuiein th'erang'e of-about 1 G0' to' 400 "F. as" anaqueous 'emulsion and concomitantly `dirrierizinig; `la 'substantial portion" of l said butadiene vto Liletlienyl'eyclohexene, separating from said `hydrocarbonmixture"4lethenylcyn clohexene produced by dimerization offbutadiene, Vforming styrene by dehydrogenation-"of `f-s'a'id i-etlf'i'eyloyclohei'iene, Land intioducingto "said polymerization `Zonefoilysiiyleneifrmed bydel hydrogenation" of l said Iill-'etheiiylcyclohexen'e'1'as the sole 'source 'ofv 'styrenec'opolymerized to -orm said highmolesula1`1weiglf1tL elastic'copolymer.

5. In a' process `for the 'produetion' ofra ihign'molecular `v`veight elastic hydioarbon :"copoly'n'ier consisting" of-b'utadi'ene and'styree wliereinfbutadiene and"'styrene are 'poly'ifri'erized'iniiderl-4 liquid 40 phase coriditions 'in' alpolymerizatio'nlzonefso as to forma hydrocarbon' mixture comprising subs't'a'iitialA amountsof saidieopolym'er, 'the improvenient Whiclicomprises' eiectingfsaidpolymerizati'ohatra temperature-inthe ralige'of 'about 100" to'fiOOo F.' and concomitantiydimerizingaportion of 1 said butadiene'to'4ethenylcyclohexene, separating from said hydrocarbon mixture avo-latile normally liquidf fraction `Y`con'iprising"LI-ethenylcyclohexene producedlby dimerization'ofbutadiene, Yformingstyrenebyoleliydrogenationfof "said normally liquidv fraction;andntro'ducing"to said polymerization zone styrene formed byidehydrogenation of said normally liquidlfraction as f atleast a portion of thestyrene'copolymerized'to form said high-molecular weight elastic copolymer.

WARREN F. FRAGHER.

#REFERENCES". `CITED -Thelfollowing` referencesare'-'of`record" in the 'file of'tliis patent:

"` UNITED "STATES 'PTE uN TS Name f Date iADutcheik` serrare- 2; Mar. l.'16, V--1948 A Number 2,438,041 

1. IN A PROCESS FOR THE PRODUCTION OF A HIGH MOLECULAR WEIGHT ELASTIC HYDROCARBON COPOLYMER CONSISTING OF BUTADIENE AND STYRENE WHEREIN BUTADIENE AND STYRENE ARE POLYMERIZED UNDER LIQUID PHASE CONDITIONS IN A POLYMERIZATION ZONE SO AS TO FORM A HYDROCARBON MIXTURE COMPRISING SUBSTANTIAL AMOUNTS OF SAID COPOLYMER, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID POLYMERIZATION AT A TEMPERATURE IN THE RANGE OF ABOUT 100* TO 400* F. IN SOLUTION IN ETHYLBENZENE AND CONCOMITANTLY DIMERIZING A PORTION OF SAID BUTADINE TO 4-ETHENYLCYCLOHEXENE, SEPARATING FROM SAID HYDROCARBON MIXTURE A VOLATILE NORMALLY LIQUID FRACTION COMPRISING ETHYLBENZENE USED AS SOLVENT AND 4-ETHENYLCYCLOHEXENE PRODUCED BY DIMERIZATION OF BUTADIENE, FORMING STYRENE BY DEHYDROGENATION OF SAID NORMALLY LIQUID FRACTION, AND INTRODUCING TO SAID POLYMERIZATION ZONE STYRENE FORMED BY DEHYDROGENATION OF SAID NORMALLY LIQUID FRACTION AS AT LEAST A PORTION OF THE STYRENE COPOLYMERIZED TO FORM SAID HIGH MOLECULAR WEIGHT ELASTIC COPOLYMER. 